The present invention generally relates to a photo switching device, and in particular to a photo switching device capable to take both alternate current and direct current and operable based on the luminance of the surroundings.
Lamps or other lighting devices are widely used to illuminate dark surroundings. Most of the lighting devices available in the market are powered by electricity. It often desired to turn off the lighting devices when the surroundings are bright, such as in the day time. This is particularly true for outdoor lighting devices for they must be turned off in the day time while turned on in the night time. An automatic switching/controlling device for the outdoor lighting device is of substantial importance in this respect.
Automatic switching devices are available in the market. However the conventional switching devices are only operable with a specific type of electricity. For example, a switching device that is designed for direct current can not take alternate current. This is because that rectifying and transforming means is required for an alternate current based switching device. The rectifying and transforming means not only complicates the overall construction of the switching device but also increases costs. Furthermore, the rectifying and transforming means makes the overall size of the switching device bulky. Such a bulky size makes it impossible to integrate itself with a control circuit of a lamp string or other lighting devices and must be provided in an independent, separate form.
Furthermore, in case that a lighting device is replaced by another one operable with different type of electricity, the switching device of the lighting device must be replaced to suit said another one of lighting device. This adds costs of part and installation to the overall expenses and limits the utilization of a specific lighting device.
It is thus desirable to provide an automatic switching device for overcoming the above-discussed problems.
Accordingly, an object of the present invention is to provide a photo switching device for a lighting device capable to take both alternate current and direct current of different voltages.
Another object of the present invention is to provide a photo switching device comprising no transformer means thereby significantly reducing the overall size and costs thereof.
A further object of the present invention is to provide a photo switching device which is capable to work with different types of lighting devices operated with different power sources.
In accordance with the present invention, a photo switching device comprises first and second terminals respectively coupled to a power source and a load. A bi-directional current routing circuit comprising a rectifying bridge is connected to the first and second terminals to receive electricity from the first and second terminals and has positive and negative output terminals. A switching/driving circuit is connected between the positive and negative output terminals for selectively conducting an output current of the bi-directional current routing circuit from the positive output terminal to the negative output terminal. The switching/driving circuit comprises a silicon controlled switching device having a gate coupled to and controlled by a controlling circuit to switch between open condition and closed condition. The controlling circuit includes a photo detecting device connected to a gate of a gate controlled device. The gate controlled device has an output coupled to and controlling the gate of the silicon controlled switching device. When the photo detecting device detects surrounding light, the output of the gate controlled device is switched from a logic high state to a logic low state which in turn changes the silicon controlled switching device from the closed condition to the open condition thereby cutting off the output current from the positive output terminal to the negative output terminal. A variable resistor is connected in serial to the photo detecting device for sensitivity adjustment. A voltage regulation circuit is combined with the controlling circuit in parallel with the photo detecting device for voltage regulation purposes.